Porous Sensor Protective Layer Anchoring
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Solution Overview
Problem
Existing gas sensors with porous protective layers face delamination and detachment issues due to thermal shock, leading to increased gas diffusion resistance and output variability, particularly at the leading end surface where adhesion is not securely maintained.
Innovation Solution
A gas sensor configuration featuring a porous leading-end protective layer that extends into a widened gas inlet portion and is fixed to the inner wall, combined with a buffer layer for enhanced anchoring, to prevent delamination and ensure adhesion to the element base, thereby improving thermal shock resistance and poisoning resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous protective layer is provided on the sensor element surface, then protection against thermal shock is improved, but delamination and detachment occur due to insufficient adhesion at the leading end surface
Solution Approach 1:
The protective layer is extended from a two-dimensional surface coating into the third dimension by forming it to protrude into the gas inlet cavity. This three-dimensional configuration increases the contact area between the protective layer and the sensor element, providing mechanical anchoring that prevents delamination and detachment during thermal shock.
Solution Approach 2:
The protective layer is pre-formed with a specific shape that protrudes into the gas inlet cavity before the sensor element is assembled into the final device. This preliminary shaping ensures that the protective layer is already positioned to maximize adhesion and protection against thermal shock before operational stresses are applied.
2Quantity of substance
If the protective layer is made porous to maintain gas diffusion, then gas permeability is improved, but structural integrity and adhesion are reduced
Solution Approach 1:
The protective layer is formed as a porous structure that allows gas molecules to diffuse through it while maintaining mechanical strength. The porosity enables gas permeability for sensor operation, while the solid matrix of the porous material provides structural integrity and adhesion to the sensor element surface.
Solution Approach 2:
The protective layer is formed as a composite structure combining porous material properties for gas diffusion with anchoring features (protrusion into the gas inlet cavity) for mechanical strength. This composite approach integrates both gas permeability and adhesion requirements into a single functional layer.
3Reliability
If the leading end surface is covered with protective layer, then thermal shock resistance is improved, but gas inlet performance deteriorates due to blocked diffusion path
Solution Approach 1:
The protective layer is formed as a porous structure that allows gas molecules to diffuse through it while maintaining mechanical strength. The porosity enables gas permeability for sensor operation, while the solid matrix of the porous material provides structural integrity and adhesion to the sensor element surface.
Solution Approach 2:
The protective layer is nested within the gas inlet cavity rather than blocking the inlet. The layer protrudes into the cavity space, creating a nested configuration where the protective function is provided without completely obstructing the gas diffusion path from the inlet to the sensor element.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses delamination and detachment of the protective layer during thermal cycles, maintaining sensor stability and responsiveness, and enhances resistance to poisoning, ensuring reliable long-term operation.
Implementation Method 1
an oxygen-ion conductive solid electrolyte
Implementation Method 2
at least one electrochemical pump cell including an outer pump electrode located on an outer surface of the ceramic body, an inner pump electrode located to face the at least one internal chamber, and a solid electrolyte located between the outer pump electrode and the inner pump electrode, the at least one electrochemical pump cell pumping in and out oxygen between the at least one internal chamber and an outside
Implementation Method 3
a heater buried in a predetermined range on a side of the one end portion of the ceramic body
Implementation Method 4
at least one internal chamber located inside the ceramic body, and communicating with the gas inlet under predetermined diffusion resistance
Implementation Method 5
a leading-end protective layer being porous, and covering a leading end surface and four side surfaces in a predetermined range of the element base on the one end portion
Data Source
AI summary
A sensor element includes: an element base including: a ceramic body made of an oxygen-ion conductive solid electrolyte, and having a gas inlet at one end portion thereof; at least one internal chamber located inside the ceramic body, and communicating with the gas inlet under predetermined diffusion resistance; an electrochemical pump cell including an electrode located on an outer surface of the ceramic body, an electrode facing the internal chamber, and a solid electrolyte located therebetween; and a heater buried in the ceramic body, and a leading-end protective layer being porous, and covering a leading end surface and four side surfaces in a predetermined range of the element base on the one end portion. The leading-end protective layer has an extension extending into a widened portion included in the gas inlet, and fixed to an inner wall surface of the widened portion.